I hate when people say something like this, or "if you can afford that fancy sports car you can afford the maintenance". The maintenance cost of hobbies like reef keeping, or having a sports car can often times add up to the cost of the tank itself, or the car itself in relatively short periods of time. $500/month is quite a lot to take on in addition to whatever other monthly bills you may have. If you look at it this way, how long would you have to save up to buy a 1,000gallon tank if you could save $500/month? Sure, you'd have to wait a couple of years but eventually you could buy one. Well, eventually that $500/month bill would more than add up to the cost of the tank setup.
I could afford to get a dodge viper, but not pay for the maintenance on one. Or I could afford to buy a large reef tank, but again, the monthly bill adder would get me in the long run.
I understand that it's easy to look at someone who has something nice like a huge tank and think they have unlimited disposable funds, but that's not often the case.